Calender stack with individually supported rolls



Sept. 9, 1958 HORNBOSTEL 2,350,952

CALENDER STACK WITH INDIVIDUALLY SUPPORTED ROLLS Filed March 13, 1956 3 Sheets-Sheet 1 L laya Horn bosze/ Sept. 9, 1958 HORNBOSTEL 2,850,952

'CALEINDER STACK WITH INDIVIDUALLY SUPPORTED ROLLS Filed March 13, 1956 5 Sheets-Sheet 2 7IIIIIIIIII k-nm Sept. 9, 1958 HORNBOSTEL 2,850,952

Q CALENDER STACK WITH INDIVIDUALLY SUPPORTED ROLLS I Filed March 13, 1956 5 Sheets-Sheet 3 L127: 12 f: T L/aya Horzzbas/e/ CALENDER STACK WITH INDIVIDUALLY SUPPORTED ROLLS Lloyd Hornbostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit, Wis, a corporation of Wisconsin Application March 13, 1956, Serial No. 571,310

Claims. (Cl. 92-75) The instant invention relates to the portion of the paper machine known as the calender or calender stack, and more particularly, to an improved multi-nip calender. Although the invention may have utility in other fields involving the pressing, smoothing, ironing or the like treatment of a strip of flexible material, a specific preferred use is in the paper machine calender. The operation of the calender in paper machines is well known and understood in the art. The purpose of the calender stack is to compact the paper to some extent and give it a fine smooth finish. This effect is obtained on both sides of the paper by the use of friction and pressure. The calender stack comprises a plurality of upright or vertically aligned calender rolls. The lowest or bottom roll of the stack is driven mechanically and it, in turn, drives the roll immediately thereabove, and so on, by friction. There is a certain amount of slip between these rolls and the result is that a substantial amount of friction acts on the paper as it passes through each of the calender nips.

The calender rolls are made of fine grained cast iron that is susceptible of a high polish, in order to give a fine finish; and it is important that these rolls be made of chilled iron. The paper web is directed first to the top roll of the stack and it passes either over the top roll and through the top nip or directly through the top nip from which it follows the next roll down to the next nip and is transferred there onto the surface of the third roll, and so on, until the web passes through the bottom nip between the bottom or king roll and the roll immediately thereabove.

In most instances, eflicient calendering of paper requires a relatively large number of nip treatments at relatively low pressures or at pressures at least sufliciently low to prevent crushing of the paper while ironing it smooth. In general, the rolls are so mounted in the ordinary calender that the entire weight of each roll rests on the roll therebelow. This is accomplished by mounting the roll so as to permit limited vertical movement. The full weight of a plurality of heavy rollers is thus applied to the paper web passing through the bottom nip in the stack; and the bottom or king roll is usually formed with a slight crown or enlarged cross-sectional area at the middle thereof in order to compensate for the deflection of the king roll downwardly which is brought about by the application of the weight of the rolls thereabove to the king roll.

As will be appreciated, the king roll is provided with fixed bearings at opposite ends thereof and when a substantial load is applied across the top of the roll, there is a tendency for the middle portion of the roll to be deflected downwardly (from the normal generally horizontal axis of the roll). For this reason, it is the general practice to have a crown of perhaps 0.01 to 0.02 inch formed in the center of the roll to compensate for the deflection. Actually, the crown may be formed so that the deflection of a given load is such as to create a substantially horizontal upper uip-defining surface for the United States Patent Patented Sept. 9, 1958 roll, or the crown may be slightly greater so as to provide somewhat greater pressures at the central portion of the nip than at the edges thereof. In any event, a particular type of paper in the ordinary calender requires a specific type of crown for a specific number of calender rolls in the stack (or for a specific weight of calender rolls in the stack).

In addition, it has now been found that another variable is introduced into the force system here involved. The bearings which support the ends of each of the calender rolls above the king roll have appreciable weight. For example, each of the bearings may weigh approximately 1000 pounds, while the roll itself may weigh approximately 10,000 pounds. In a typical paper machine the diameter of the king roll may be about 40 inches and the diameter of each of the rolls stacked thereabove may be about 18 inches. All of the rolls have an axial dimension that is the width of the paper machine which in modern-day machines may be as much as 20 to 25 feet. Since the rolls are supported through the bearings at the extremities thereof there is, of course, a tendency for each roll to be deflected downwardly slightly at the cen-' tral portion thereof by virtue of the weight of the roll.- As will be appreciated, if the king roll has a slight crown in its normal configuration, a slight downward deflection of the kind roll in the middle portion thereof (in order to support the weight of all of the rolls stacked thereon) may result in a substantially horizontal nip-defining top surface for the king roll. This is so if there is a precise correlation between (1) the contour of the crown, (2) the number of stacked calender rolls (or the weight thereof), and (3) the particular web being processed in the calender. If these factors are not carefully correlated, it will be appreciated that defective operation of the calender may result. The diificulty here is that calenders are preferably adapted for a number of different operations, which operations cannot be varied without careful variation of the factors just mentioned so as to obtain the proper correlation therebetween. Moreover, it has been found that the weight of the bearings, or the weight which the bearings apply to the extremities of each calender roll is a fourth factor which materially affects the operation of the calender stack.

The instant invention resides in a unique structural concept which permits a great deal of flexibility in operation in a given calender stack and which permits unique control of the load forces and the distribution thereof across the calender. This is accomplished by providing individual load relieving means for each bearing, with such load relieving means supported independently on a frame or similar structure member, rather than being supported by the bearing immediately therebeneath or being carried by the roll itself. It is further important to note that each bearing is so supported and not merely the bearings of perhaps a single intermediate roll in the stack as well as the king roll.

It is, therefore, an important object of the instant invention to provide an improved calender stack arrangement.

Another important object of the instant invention is to provide an improved multi-nip calender comprising a stack of calender rolls mounted-in a calender frame and supported by bearings at opposite ends thereof, which in turn are independently supported by the frame.

Other and further objects, features and advantages of the instant invention will become apparent to those skilled in the art from the following detailed disclosure of a preferred embodiment thereof as shown in the drawings attached hereto and made a part hereof.

On the drawings:

Figure 1 is a diagrammatic illustration showing a stack pf rolls and illustrating in exaggerated form the manner .3 in which such rolls may be deflected during improper correlation between the essential controlfactorsjn a calender stack of the prior art;

Figure 2 is a diagrammatic illustration similar to Figure 1,; but showing how-the rollsmaybe-positioned with properrdefiectionusing the principles of the instant inve on;

Figure 3-isa viewcomparable -to Figure 2 showing another arrangement of the rolls which maybe accomplished using the principles of the instant invention;

Figure 4 is a fragmentary top plan view of a bearing mounting employed in thewpractice of the instant invention;and

Figure 5 is aside elevational view of a calenderstack embodying the instant invention.

As shown on the drawings:

. In'Fjgure l, a bottom portion of a calender stack, indicatedgenerally bythe reference numeral 10, is shown comprising a king roll 11 at the. bottom mounted on suitable bearings 12 and 13 which are in turn firmly secured to a fixed mounting such as a floor F. Immediately above the king roll 11 .is. a calender roll 14 which, in turn, is mounted for rotation in bearings 15 and 16. Above the calender roll .14 is another calender roll 17 which, in turn, is mounted for rotation on bearings 18 and 19 mounted at the extremities thereof. On one side of the, stack the bearings 12,. 15 and 18 are mounted with one immediately above the other; and on the other side of thestack. the bearings 13,16 and 19 are similarly mounted.

,As will be .noted, the axis x-11 for the roll 11 is deflectednownwardly below a horizontal or center line 0-11 at therniddle of the roll 11 and this is caused by the load applied to the roll 11 by the weight of the rolls 14 and 17 (and any rolls thereabove). In the calender 10, however, the central portion of the top surface of theroll 11 is still crowned so as to extend a distance R-ll above the outer extremities of the roll '11, and the bottom surface of the roll 11 is downwardly bowed still a greater distance D-11.

The amount of operating crown R-11 depends upon the mount of original crown formed in the roll 11 plus the total weight of the calender stack of rolls 14, 17, etc. mounted thereabove. As will be appreciated, if it is desired to operate a calenderwith substantially no operating crown (R-ll) in the king roll 11, the initial crown in the king roll 11 and the total weight of calender rolls 14, 17, etc. are correlated so as to obtain substantially no operating crown. If, however, it then becomes desirable to make a change in theoperation of'the prior art calender by using less calender rolls in the stack, then a greater operating crown R-11 will'- be obtained. This may possibly result in an undesirable pressure distribution at-the-portion of the web W passing through the nip N-l. In addition, the bearings 15 and 16 apply an extra load at the opposite edges of the Web W passing through the nip -N-11 (if these bearings are mounted for limited vertical movement). This may also be undesirable because it will result in excessive pressures at the outer edges of the web W. In either case an undesirable distribution of load forces at -the nip N-l may be obtained. By substitution of a different king roll for the king roll 11, with a different crown, it may be possible to avoid some of the non-uniform distribution, but this is anexpensive procedure. Also,--this procedurewill not necessarily relieve the excessiveweight that is applied to the opposite edges of the web W because of the bearings 15 and 16. If the bearings 15 and 16 are supported, as for example on the bearings 12 and 13, then the relative positionsof the bearings will be fixed and this must bechanged each time any change in operating conditions is involved (such as changes in the web itself), which is also an undesirable arrangement. Also, if all of the movable bearings, such as the bearings 15 and 18 are connected on one side of the calender 10, the amount of 4 bearing weight applied at the opposite extremities of the roll 14 is that much greater.

In actual practice, the king roll 11 is crowned slightly so that a definite operating crown 11-11 results when an entire load of a predetermined number of calender rolls 14, 17, etc. is applied. This then results in a slight upward bending of the middle of the immediately adjacent roll 14. The weight ofthe bearings 15 and 16 is, of course, applied primarily. along the opposite edges of the web W at the nip N 1,, but the forces resisting upward bending of the middle of the roll 14 apply a compensating load to the middle of the web, so that with careful correlation between bearing weight, total calender stack weight,. and .;crown it .is possible to obtain substantially uniform pressuresracross the full width of the nip N4. Any change in operating conditions, such as the change in the number of rolls in the stack, will obviously disrupt this delicate balance; other than becomes necessary to employ av different. crown .tor the, king roll 11.

Referring now-to Figure 2, wherein reference numerals designating;substantiallythe same structure as that shown in Figure 1; are indicated-bythesame reference numerals followed by the.letter fa, it will be seen that a king roll 11a is provided with a slight operating crown- R-lla. The operating crownR-lla varies with the number of rollswl4a; 17a,cetc. in the stack. Comparing Figures 1 and 2 itis apparent that the operating crown R-lla is smaller than the operating crown R-11 and this would presumably result in greater pressures at the edges of the nip N-la than in. the middle in the calender 10:: (if the bearings 15a and 16a weigh the same as the bearings 15. and 16). In the practice of the instant invention, however, resilientmeans indicated diagrammatically at 20a and 21a are provided to urge the bearings 15a and 16aupwardly. Inthis -way it is possible to readily adjustthe load-which thebearings 15a and 16a apply at the edges of the-web Wain the nip N-la. In effect, the weight of the bearings 15a and 16a is varied'so as to adjust to the crown R-lla and thus result in uniform nip pressures throughout the full width of the web W11. Resilient means 22a and 23a are, likewise, provided for the bearings 18a and 190, respectively. And in the case of each and every roll in the calender stack ltla in-- dependent resilient mounting means are provided urging each of the bearings up independently so as to effectively control the load applied by each of the bearings. In this way, calender rolls may be added to or taken from the calender 10a and'the resulting-differences in the operating crown R-lla can be compensated for in each instance.

Since there is a distinct operating crown R-11a shown in Figure 2, it will be appreciated that the resilient means 20a and 21a do not relieve entirely the load applied by the bearings 15a and 16a, but only partially compensate therefor.

Referring now to Figure 3, wherein reference numerals designating substantially the same structure as that shown in Figures 1 and 2 are indicated by the same reference numerals followed by the letter b," it will be seen that the king roll llbhas no operating crown. In this situation, -the;load of the calender rolls 14b and 171: has been ,just sufiicient to completely overcome the original crown in the king roll 11b. Since no operating crown is employed, it will be appreciated that the bearings 15b and 16b supporting the roll 14b cannot be permitted to apply any load to the web Wb in the nip N-lb. For this reason the resilient means 20b and 21b must completely relieve the load of the bearings 15b and. 16b, respectively. it will be appreciated that, even if the king roll 11]) were to be so heavily loaded that there would be a negative crown, it would be possible to apply such force through the resilient means 20b andZlb that there would be a tendency to bow the roll 14b downwardly and compensate even for this negative'crownu However, since itis generally preferable to operate with at least a slight positive crown on the king roll, the instant arrangement preferably involves a structure wherein each of the bearings is supported in part (cantileverly) by the roll attached thereto and in part by resilient means urging the roll upwardly.

Referring now to Figures 4 and 5, wherein reference numerals designating substantially the same structure as that shown in Figures 1, 2 and 3 are indicated by the same reference numeral followed by the letter d, it will be seen that the views of Figures 4 and 5 may be considered as being taken looking toward the calender d from the right-hand side for the views 1, 2 and 3. The calender 10d is provided with a main upright frame member 24d, structurally connected to a cross beam 25d to another upright supporting member 26d (shown only partially) the supporting member 26d carries the last drier roll 27d, shown in dotted lines, and the web Wd travels from the drier roll 27d under a guide roll 28d over a guide roll 29d and between the top calender rolls 30d and 31d of the calender 10d.

Calender rolls 14d, 17d, and 30d-36d are mounted in superimposed position on the king roll 11d. As indicated, the king roll bearing 13d is fixedly mounted on the supporting floor Fd. For the purposes ofsimplification reference hereinafter is made only to the bearings and associated structure here shown on the right-hand side of the calender 10d, although it will be appreciated that substantially identical structure appears on theiopposite side of the calender 10d. The bearings 16d, 19d. and 37-43, inclusive, for the remaining calender rolls are swingably carried about the pivot pins P, P, etc. each independently mounted on the frame 24d, so that each bearing is freely swingable about its pivot pin P, substantially independently of the other bearings. The overhead lifting links L, L, etc. are provided to permit limited vertical movement of each of the bearings, but for the purpose of lifting all the bearings when such is desired during shut down or repair.

Referring now to the details of Figure 4, it will be seen that each of the bearing mountings is the same and for the bearing 16d there is provided a housing 44d which is fixedly secured to an arm 45d swingable about the pivot P which is fixedly mounted on the upright frame member 24d. The arm member 45d extends between the pivot P and the bearing housing 44d and also has a rearward extension 46d which extends around and behind the frame member 24d. This arm member 46d forms a part of the resilient load relieving means 21d hereinbefore shown diagrammatically. A frame member 47d is fixedly secured to the back of the main upright frame 24d, as by welding, and provides a downwardly facing ledge 48d. The ledge 48d mounts a diaphragm element indicated generally by the reference numeral 49d. The diaphragm 49d is of standard construction, comprising a resilient yieldable diaphragm element 50d peripherally clamped between the ledge 48d and a mating member 51d. The diaphragm member 50d and the ledge 48d define a pressure chamber 52d. A fluid such as air under pressure is controllably fed from a source indicated diagrammatically at S through a control valve V and into the chamber 52d. The rear extremity 53d of the arm member 46d is connected to the movable diaphragm element 50d by a rod 54d clamped to the diaphragm element 50d in the customary manner and adjustably secured to the arm extremity 53d through a lock nut 55d. As indicated, the diaphragm element 51d in its connection with the arm extremity 53d are standard structures in the art need not be further described herein. In essence, movement of the flexible diaphragm element 50d causes vertical movement of the drive rod 54d which in turn moves the arm extremity 53d. Weight of the bearing 16d tends to drive the rod 54d upwardly and the air pressure in the chamber 52d tends to drive the rod 54d downwardly. In this way controlled air pressure in the chamber 52d may be used to relieve a part of the load caused by the weight of the bearing 16d, all of such load, or even more than this load, depending upon the operating conditions desired. The same load relieving structure is employed for each of the roll bearings for the calender rolls mounted above the king roll 11d. Independent control means such as the valve V are also provided for each load relieving device 21d, 23d, etc.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a paper machine, a multi-nip calender comprising a calender frame, a stack of calender rolls in the frame including a bottom roll and a plurality of superimposed rolls, separate and independent bearings rotatably carrying the ends of each of said superimposed rolls, and separate and independent means for each of said bearings carried by said frame and urging each of said bearings upwardly.

2. In a paper machine, a multi-nip calender comprising a calender frame, a stack of calender rolls in the frame including a bottom roll and a plurality of superimposed rolls, separate and independent bearings rotatably carrying the ends of each of said superimposed rolls and swingably mounted on said frame to permit limited vertical movement of each roll independently of the other rolls, and separate and independent means for each of said bearings carried by said frame and urging each of said bearings upwardly.

3. In a paper machine, a multi-nip calender comprising a calender frame, a stack of calender rolls in the frame including a bottom roll and a plurality of superimposed rolls, separate and independent bearings rotatably carrying the ends of each of said superimposed rolls and swingably mounted on said frame to permit limited vertical movement of each roll independently of the other rolls, and separate and independent fluid pressure responsive means for each of said bearings carried by said frame and urging each of said bearings upwardly.

4. In a paper machine, a multi-nip calender comprising a calender frame, a stack of calender rolls in the frame including a bottom roll and a plurality of superimposed rolls, independent mounting and driving means for said bottom roll, independent mounting means for each of said superimposed rolls rotatably supporting the ends thereof, independent means carried by said frame connected to each of said mounting means for adjusting the posit-ion of each roll relative to the rolls immediately above and below, and fluid pressure means actuating said adjusting means independently of each other.

5. In a paper machine, a multi-nip calender comprising a calender frame, a stack of calender rolls in the frame including a bottom roll and a plurality of superimposed rolls, separate and independent bearings rotatably carrying the ends of each of said superimposed rolls, and individual arm connected to each of said bearings and pivotally connected to said frame, and separate and independent means for each of said arms carried by said frame and urging each of said bearings upwardly.

References Cited in the file of this patent UNITED STATES PATENTS 1,925,949 Case Sept. 5, 1933 1,934,233 Malkin Nov. 7, 1933 2,312,726 Munro Mar. 2, 1943 2,364,443 Hornbostel Dec. 5, 1944 

